1. Field of the Invention
The present invention relates to circuit modules, and more particularly to a circuit module including multiple core isolators.
2. Description of the Related Art
A known isolator is, for example, a non-reciprocal circuit element described in Japanese Unexamined Patent Application Publication No. 2006-311455. This non-reciprocal circuit element includes a ferrite having a pair of principal surfaces that oppose each other, multiple center electrodes, permanent magnets having principal surfaces that oppose the principal surfaces of the ferrite, and a circuit board. The multiple center electrodes are formed of a conductor film on the principal surfaces of the permanent magnets so as to intersect each other and be insulated from each other. The center electrodes are also electrically connected to each other via intermediate electrodes formed on edge surfaces that are orthogonal to the principal surfaces of the ferrite. Further, both of the ferrite and the permanent magnets are arranged on the circuit board in such an orientation that the principal surfaces thereof are orthogonal to a surface of the circuit board. The non-reciprocal circuit element as described above is used in, for example, a communication apparatus.
Recently, as a demand for reductions in size of a communication apparatus arises, a demand for reductions in size of a non-reciprocal circuit element has been increased. Accordingly, removal of a yoke for suppressing leakage of magnetic flux to the outside has been proposed for the non-reciprocal circuit element described in Japanese Unexamined Patent Application Publication No. 2006-311455.
However, when the yoke is removed from a non-reciprocal circuit element, magnetic flux leaks from around the non-reciprocal circuit element. Since a communication apparatus has multiple non-reciprocal circuit elements mounted therein, when the leakage of magnetic flux occurs, the non-reciprocal circuit elements are magnetically coupled with each other. As a result, the characteristics of the non-reciprocal circuit elements are changed.